The performance of various types of electronic equipment such as mobile phones and personal computers has been improved. In addition, such electronic equipment has been increasingly miniaturized. With such improved techniques, the amount of heat generated by electronic devices increases. Thus, there has been a demand for a new cooling technique for implementing small-sized high-performance equipment.
A technique has been proposed which uses a metal core substrate containing metal with a high heat conductivity instead of a heat sink in order to improve the heat dissipation capability of the electronic equipment without hindering the miniaturization thereof (see, for example, Japanese Patent Laid-Open No. 2004-311849). The metal core substrate is normally exposed at the outer edge of the wiring substrate. Heat from the metal core substrate is dissipated from this exposed portion to the exterior.
However, the heat dissipation capability (heat diffusion capability) of the metal core substrate is still insufficient to apply the metal core substrate to small-sized electronic equipment, which generate a particularly large amount of heat. Thus, a relatively large-sized heat sink or heat pipe or the like needs to be connected to the metal core substrate exposed at the outer edge of the wiring substrate. This disadvantageously hinders the miniaturization of electronic equipment.